Chemistry - Complete d-block Question with Solution | TestHub

On  treating sulphite (${\mathrm{SO}}_3^{2-}$) with warm dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$, ${\mathrm{SO}}_2$  gas is evolved which is suffocating with the smell of burning sulphur.

${\mathrm{Na}}_2{\mathrm{SO}}_{3 } + {\mathrm{H}}_2{\mathrm{SO}}_{4 }\to {\mathrm{Na}}_2{\mathrm{SO}}_4 + {\mathrm{H}}_2\mathrm{O} + {\mathrm{SO}}_2$

The gas turns potassium dichromate paper acidified with dil. ${\mathrm{H}}_2{\mathrm{SO}}_4$, green.

${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7 + {\mathrm{H}}_2{\mathrm{SO}}_{4 } + 3{\mathrm{SO}}_2 \to {\mathrm{K}}_2{\mathrm{SO}}_4 + {\mathrm{Cr}}_2({\mathrm{SO}}_4{)}_3 + {\mathrm{H}}_2\mathrm{O}$